1. Field of the Invention
This invention relates broadly to the field of containers, such as the plastic containers that are commonly used for packaging solid and liquid detergents, cleaners and foodstuffs. More specifically, this invention pertains to an improved process for making a dual chambered container that is lightweight, strong and inexpensive to produce.
2. Description of the Prior Art
Plastic containers are in wide use throughout the United States and the world for packaging virtually every type of liquid and solid material, for both commercial and household applications. The detergent industry, for example, has turned increasingly to plastic containers for packaging such products as bleach, soap, sanitizing agents, and polishes. Plastic is relatively inexpensive, will not shatter when dropped, and is recyclable.
Some products are best packaged, for reasons of both marketability and convenience, together with one or more other products in a container that has more than one chamber, or in a pair of containers that are joined together in some manner. With respect to the latter mentioned option, packaging is known that includes two separate containers that are joined together by a common closure having two openings. U.S. Pat. Nos. 5,289,950 and 5,252,312 disclose packaging of this type. These type of containers are relatively expensive to make because of the complexity of the manufacturing process, require a relatively large amount of plastic material per volume of product that is being packaged, and are undesirable to the extent that the container""s design leaves open the possibility of separation of the individual containers during use.
A basic process for producing plastic containers is through extrusion blow molding. Like other types of molding, the object of the process is to produce a hollow item via air inflation of a parison. The blow molding process involves first heating the parison, a preshaped sleeve of plastic, usually made by extrusion. The heated parison is engaged in a mold cavity formed by two mold halves and inflated with air delivered through a blow pin or needle. As the parison is inflated, it takes on the shape of the mold cavity. The polymer quickly solidifies upon contacting the cold mold, and the finished hollow article is ejected from the mold.
Other known processes for producing a plastic container having more than one chamber include those where a container is first molded as a single chambered container, and then heat sealed into separate compartments in a subsequent reforming step. Because of this second reforming and heating step, the process is more time consuming and expensive than a one-step forming process. In addition, because the compartments that are defined by the heat sealing step tend to be joined together only by a thin web of material, the resulting product tends to be overly flexible and requires reinforcement by and external device such as a special closure, a base cup or an adhesive label that is positioned to prevent relative movement between the formed compartments.
A need exists in this area of technology for an improved process for making an improved multi-chambered container that is lightweight, relatively inexpensive to produce, and that requires less external reinforcement against flexure than conventional multi-chambered containers do.
Accordingly, it is an object of this invention to provide an improved process for making an improved multi-chambered container that is lightweight, relatively inexpensive to produce, and that requires less external reinforcement against flexure than conventional multi-chambered containers do.
In order to achieve the above and other objects of the invention, a molding process is provided for making a plastic container that has more than one chamber and that is constructed so as to be stiffer than conventional molded multi-chambered containers. According to a first aspect of the invention, a parison is heated and inflated to form the container. Further, first and second pinched-in areas are fashioned in the sidewall of the container. The first pinched-in area includes first and second wall portions that extend inwardly toward an interior of the main body of the container, and a first end wall portion connecting the first and second wall portions. The second pinched-in area includes third and fourth wall portions that extend inwardly toward an interior of the main body, and a second end wall portion connecting the third and fourth wall portions. The first end wall portion is joined to said second end wall portion so as to define separate compartments within said main body, and wherein the first end wall portion is laterally offset from the second end wall portion, whereby the flexibility of the main body about the joint of the first and second wall portions is minimized. In the next step, the container is cooled.
According to a second aspect of the invention, the heated parison is inflated at the same time the pinched-in areas are fashioned. According to an additional aspect of the invention, the molding process is extrusion blow molding. According to another aspect of the invention, the mold used to make the container has pinch ribs extending into a mold cavity for forming the pinched-in areas.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.